Bactericidal effect of sparfloxacin alone and in combination with amoxicillin against Streptococcus pneumoniae as determined by kill-kinetic studies

Ten clinical isolates of Streptococcus pneumoniae (six intermediately penicillin-sensitive, one penicillin-resistant and three penicillin-sensitive strains) were studied by kill-kinetic experiments using sparfloxacin alone and in combination with amoxicillin. Equipotent doses of the antibiotics (1x, 2x and 4x the MIC) were used in the kill-kinetic studies. Sparfloxacin had a moderate bactericidal potential at 4x: MIC after 5 h and the combination with amoxicillin did not significantly increase its bactericidal activity. The clinical significance of these findings warrants further studies in vivo.